#include <string.h>
#include <malloc.h>
#include "lceb.h"

unsigned ncombinations(nops, len)
    int nops, len;
{
    int result = 1;
    while(len > 0){
        if(len & 1)
            result *= nops;
        nops *= nops;
        len >>=1;
    }
    return result;
}

char *combination(ops, len, n)
    char *ops;                                    /* string to combine */
    int len;                                      /* len of result */
    int n;                                        /* iteration # */
{
    static char *res=NULL;
    static int len_ops;
    int i;

    if (!res) {                                   // 1st call
        len_ops=strlen(ops);
        res=malloc(len * sizeof(char) + 1);
    }
    for(i=0; i<len; ++i){
        res[len -i -1] = ops[n % len_ops];
        n /= len_ops;
    }
    return res;
}

#ifdef STANDALONE
int main(ac, av)
    int ac;
    char **av;
{
    char *ops="+-*/", *p;
    int len_ops=strlen(ops);
    int i, j, nops, ncombs;

    nops=atoi(*(av+1));
    ncombs=ncombinations(len_ops, nops);
    printf("# operators combinations : %d\nlist = ", ncombs);
    for (i=0; i<ncombs; ++i) {
        p=combination(ops, nops, i);
        printf("[%s]\n", p);
        //for (j=0; j<4; ++j)
        //    distribute(j, p);
        //printf("\n");
    }
}
#endif